Trilobite

Trilobites represented very numerous group of marine arthropods with many thousand species. All species are now long extinct since they lived from Kambrian to Permian periods. Their body is protected by strong dorsal exoskeleton divided longitudinally and transversally in three sections, thereof their name. The body can be functionally divided in three sections: cephalon, thorax and pygidium. Cephalon has two eyes that are usually compound (like modern insects have). They can be imagined as clusters of tiny single eyes with their numbers reaching thousands.Thorax consists of several articulated segments with pairs of walking legs. Trilobites were usually several centimeters long, but there were exceptions reaching only several millimeters in length or on the other hand gigants 70 cm long. Majority of them lived at the bottom of shallow seas scavenging for small organic particles, only few of them were predators. Some species were able to curl in a protective ball if threatened. They also possessed quite complex array of dorsal spines that bristeled up when trilobites curled.